1. Field of the Invention
This invention relates to automatic door closures, and more particularly to pneumatic door closures as used in domestic applications on screen and entrance doors.
2. Description of the Prior Art
It is well known in the art that various problems and difficulties are being encountered in providing suitable means for automatically closing doors, particularly those devices that are operated pneumatically.
Various types of closure devices have been tried and used, but very often they include features that restrict their use, and are constructed so as to be complicated to mount and operate, as well as expensive to maintain.
It has further been found in practice that the commonly used aluminum closures are difficult to adjust and set at given points of extension. This difficulty is generally caused by the lack of a properly designed control-washer device provided for this purpose. The aluminum closures are thus easily damaged and rendered defective by improper striking on the side of the tubular unit housing.
Further, quality in production and function is uncertain as a result of difficulty in maintaining the bore tolerances in the extrusion from which the cylindrical tube is manufactured.